Light source unit, lighting apparatus and image projection apparatus

ABSTRACT

A light source unit includes a first reflector having a reflection face; a second reflector having a reflection face; a plurality of light sources; and a light condensing optical system to condense light emitted from the plurality of light sources. Light beams emitted from the plurality of light sources are reflected at a first reflection position on the reflection face of the first reflector, and then reflected at a second reflection position on the reflection face of the second reflector. The second reflection position is close to an optical axis of the light condensing optical system compared to the first reflection position.

This application claims priority pursuant to 35 U.S.C. §119 to JapanesePatent Application Nos. 2013-052023, filed on Mar. 14, 2013 and2014-038813, filed on Feb. 28, 2014 in the Japan Patent Office, thedisclosures of which are incorporated by reference herein in theirentirety.

BACKGROUND

1. Technical Field

The present invention relates to a light source unit having a pluralityof light sources, a lighting apparatus having the light source unit, andan image projection apparatus employing the lighting apparatus.

2. Background Art

Screen images of personal computers, video images, and image data storedin memory cards can be transmitted to image projection apparatuses knownas projectors that can project images onto a screen. Theses imageprojection apparatuses include a lighting unit using a high-intensitydischarge lamp (e.g., super high-pressure mercury lamp) as light source.The discharge lamp can emit high-intensity light with low cost, butneeds a given time to stably emit light after turning ON the lamp. Inview of such issues of the discharge lamp, as alternative light sourceof the discharge lamp, a solid light emitting element such as a lightemitting diode (LED), a laser diode (LD) of red (R), green (G), and blue(B), or organic electroluminescence (OEL) have been developed as thelight source.

By using the solid light emitting element as the light source ofprojectors, high-speed activation of projectors can be devised, andenvironmental burden can be reduced. The light source unit using thesolid light emitting element may include, for example, a first lightsource (excitation light source) such as a blue laser diode andfluorescent material, in which a laser beam emitted from the blue laserdiode as a excitation light is irradiated to the fluorescent material,with which the fluorescent material is excited to generate light of R,G, B, and the R, G, B light is modulated for gradation for each pixelusing a light modulation element such as a digital micro-mirror device(DMD) to generate a color projection image.

In the image projection apparatuses using the laser diode as the lightsource, how to secure light quantity becomes an important issue, and ithas been proposed to arrange a large number of laser diodes in a matrixpattern on a plane or to arrange a large number of laser diodes denselytwo-dimensionally.

For example, one configuration is disclosed for synthesizing lightemitted from a plurality of light sources arranged on a plane with rowsand columns, in which a plurality of rectangular reflection mirrors isarranged in a step-like pattern to shorten an interval between lightflux emitted from light source in each row, and to shorten an intervalbetween light flux emitted from light source in each column.

If a large number of light sources (e.g. laser diodes) are arranged aslaser sources, light emitted from each light source (e.g. laser diode)is required to be focused at a substantially one point in view ofcompact size of a light-transmission optical system and higher lightefficiency.

If a distance from the laser sources (light sources) to a light focuspoint is set small, a light entering angle at the light focus pointbecomes greater, and light use efficiency at later optical parts becomeslower and a size of optical system becomes greater.

By contrast, if a distance from the laser sources (light sources) to alight focus point is set great, fluctuation of the light focus pointbecomes greater due to tolerance of laser, light emitting point andoptical system, with which efficient use of light emitted from the lightsource at later optical parts becomes difficult. This could be solved byincreasing a lens diameter, but a greater lens increases the size ofoptical system

In the above configuration, a cross-section area of light flux isreduced by synthesizing light beams using the reflection mirrors.Because a plurality of reflection mirrors are used to synthesize lightbeams, setting and adjustment of each mirror is required, and a spacefor arranging a plurality of reflection mirrors in the step-like patternis required, with which a compacting of size of light source unitbecomes difficult.

SUMMARY

In one aspect of the present invention, a light source unit is devised.The light source unit includes a first reflector having a reflectionface; a second reflector having a reflection face; a plurality of lightsources; and a light condensing optical system to condense light emittedfrom the plurality of light sources. Light beams emitted from theplurality of light sources are reflected at a first reflection positionon the reflection face of the first reflector, and then reflected at asecond reflection position on the reflection face of the secondreflector. The second reflection position is close to an optical axis ofthe light condensing optical system compared to the first reflectionposition.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages and features thereof can be readily obtained and understoodfrom the following detailed description with reference to theaccompanying drawings, wherein:

FIG. 1 is a schematic side view of a light source unit according to afirst example embodiment;

FIG. 2 is a schematic front view of a light source assembly of the lightsource unit of FIG. 1;

FIG. 3A is a schematic side view of a light source unit with a holdingstructure according the first example embodiment;

FIG. 3B is a schematic front view of the light source unit of FIG. 3A;

FIG. 4 is a schematic side view of a light source unit according to asecond example embodiment;

FIG. 5 is a schematic side view of a light source unit according to athird example embodiment ;

FIG. 6 shows a light path when a coupling lens of a light source of alight source unit of the first example embodiment is shifted;

FIG. 7 shows a light path when a coupling lens of a light source of alight source unit of the second example embodiment is shifted;

FIG. 8 shows a light path when a coupling lens of a light source of alight source unit of the third example embodiment is shifted;

FIG. 9A shows a condition of light focus point for the light source unitof FIG. 1;

FIG. 9B shows a condition of light focus point for the light source unitof FIG. 6;

FIG. 10A shows a condition of light focus point for the light sourceunit of FIG. 4;

FIG. 10B shows a condition of light focus point for the light sourceunit of FIG. 7;

FIG. 11A shows a condition of light focus point for the light sourceunit of FIG. 5;

FIG. 11B shows a condition of light focus point for the light sourceunit of FIG. 8;

FIG. 12 shows parameters of optical system of the first exampleembodiment;

FIG. 13 shows parameters of optical system of the second exampleembodiment;

FIG. 14 shows parameters of optical system of the third exampleembodiment; and

FIG. 15 is a schematic configuration of a lighting apparatus and animage projection apparatus having a light source unit.

The accompanying drawings are intended to depict exemplary embodimentsof the present invention and should not be interpreted to limit thescope thereof. The accompanying drawings are not to be considered asdrawn to scale unless explicitly noted, and identical or similarreference numerals designate identical or similar components throughoutthe several views.

DETAII ED DESCRIPTION

A description is now given of exemplary embodiments of the presentinvention. It should be noted that although such terms as first, second,etc. may be used herein to describe various elements, components,regions, layers and/or sections, it should be understood that suchelements, components, regions, layers and/or sections are not limitedthereby because such terms are relative, that is, used only todistinguish one element, component, region, layer or section fromanother region, layer or section. Thus, for example, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the present invention.

In addition, it should be noted that the terminology used herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of the present invention. Thus, for example, asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Moreover, the terms “includes” and/or “including”, when usedin this specification, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Furthermore, although in describing views shown in the drawings,specific terminology is employed for the sake of clarity, the presentdisclosure is not limited to the specific terminology so selected and itis to be understood that each specific element includes all technicalequivalents that have a similar function, operate in a similar manner,and achieve a similar result. Referring now to the drawings, apparatusesor systems according to example embodiments are described hereinafter.

First Example Embodiment

FIG I is a schematic side view of a light source unit 1 according to afirst example embodiment, and FIG. 2 is a schematic front view of lightsources included in the light source unit 1. For the simplicity of thedrawing, FIG. 1 shows a configuration of disposing two light sources,but the light source unit 1 can be disposed with a plurality of lightsources as shown in FIG. 2 such as ten light sources. Further, FIG. 2shows a configuration of light sources and coupling lenses.

The light source unit 1 includes, for example, a light source assembly2, a condensing lens L1, a first reflection mirror 10 and a secondreflection mirror 9. The light source assembly 2 includes a plurality oflight sources 11-1 to 11-10 and a plurality of coupling lenses 12-1 to12-10 arranged in a circle pattern two dimensionally. The condensinglens L1 is used as a light condensing optical system to generateconverging light from light beams emitted from each one of light sourcesin the light source assembly 2, in which the converging light isgenerated while reducing a cross-section area of light beams towards thecenter of circle. The first reflection mirror 10 is used as a firstreflector, and the second reflection mirror 9 is used as a secondreflector. The plurality of light sources 11-1 to 11-10 and theplurality of coupling lenses 12-1 to 12-10 are disposed with aconcentric circular pattern (FIG. 2) about an optical axis of thecondensing lens L1 (long-dashed/short-dashed line in FIG. 1).

Compared to the second reflection mirror 9, the condensing lens LI isdisposed at a position closer to the light sources 11-1 to 11-10.Specifically, as shown in FIG. 1, the plurality of light sources 11-1 to11-10, the plurality of coupling lenses 12-1 to 12-10, the condensinglens L1, the second reflection minor 9, and the first reflection mirror10 are arranged in this order from the left (or light source side) tothe right (light exit side) in the light source unit 1.

Each of the plurality of light sources 11-1 to 11-10 is, for example, asemiconductor laser such as a laser diode, and color of each lightemitted from the light source assembly 2 may be the same color, ordifferent color with each other. Each of the plurality of couplinglenses 12-1 to 12-10 is a convex lens made of glass or plastic. Thelight sources 11-1 to 11-10 and the respective coupling lenses 12-1 to12-10 are being faced each other so that the optical axis of the lightsources 11-1 to 11-10 and a curvature center axis of the respectivecoupling lenses 12-1 to 12-10 are aligned with each other. Each of thecoupling lenses 12-1 to 12-10 includes a collimator lens that converts alight emitting from the light source to parallel light or converginglight.

By arranging the light sources 11-1 to 11-10 and the coupling lenses12-1 to 12-10 in the above described configuration, light emitted fromeach one of the light sources 11-1 to 11-10 passes through therespective coupling lenses 12-1 to 12-10, facing the respective lightsources 11-1 to 11-10, and then enters the condensing lens L1.

Then, by using a single condensing lens such as the condensing lens L1facing the coupling lenses 12-1 to 12-10, a substantiallyconically-shaped light slanted toward the center of the circle withrespect to the first reflection mirror 10 is generated. Because thelight source assembly 2 is configured with a combination of the lightsources 11-1 to 11-10 and the coupling lenses 12-1 to 12-10 that canconvert light emitted from the light sources 11-1 to 11-10 to parallellight or converging light, even if light emitted from the light sources11-1 to 11-10 is diverging light, the light emitted from the lightsources can be efficiently used by passing the light through thecoupling lenses 12-1 to 12-10.

As shown in FIG. 3A, the first reflection mirror 10 has a reflectionface 10 a, and the second reflection mirror 9 has a reflection face 9 a,and the first reflection mirror 10 and the second reflection mirror 9are arranged to face the reflection face 10 a and the reflection face 9a with each other. In an example embodiment, each of the firstreflection mirror 10 and the second reflection mirror 9 is a singlereflection mirror.

As shown in FIG. 3A, the light sources 11-1 to 11-10, the couplinglenses 12-1 to 12-10, the condensing lens Ll, the second reflectionmirror 9 and the first reflection mirror 10 are supported by a supporter30 using retaining parts 31, 32, 33, 34, 35 formed for the supporter 30.FIG. 3B is a front view of FIG. 3A. In FIG. 3B, the first reflectionmirror 10 is omitted for the clarity of drawing.

The supporter 30 can be made of, for example, metal such as aluminum andmolding resin, and the supporter 30 can be formed with the retainingparts 31 to 35 integrally, or the supporter 30 and the retaining parts31 to 35 can be formed separately and then bonded together as anintegral part.

The first reflection mirror 10 is made from a parallel plate such as aglass plate. A reflection face 10 a, used as a reflection mirror, can beformed on one face of the first reflection mirror 10 by depositingsilver film or dielectric multilayer such as aluminum layer on one faceof the first reflection mirror 10. The first reflection mirror 10 isretained in the supporter 30 by the retaining part 35.

The first reflection mirror 10 includes a light passing portion forpassing light beams. The light passing portion may, for example, be anopening part 10 b set at the center portion of the first reflectionmirror 10, wherein the opening part 10 b is formed, for example, as athrough hole. Alternatively, the light passing portion can be formedwithout forming an opening such as a through hole. For example, thelight passing portion can be formed by depositing an aluminum layer on aglass plate while not depositing aluminum at a position corresponding tothe opening part 10 b, which means that the aluminum layer is formedwith a ring pattern on the glass plate, and the center portion of thering pattern not formed with the aluminum layer can be used as atransparent portion that can be used as an alternative of the openingpart 10 b, in which processing cost for a through hole can be saved. Asabove described, the light passing portion can be formed on thetransparent plate, or can be formed as a through hole that the light canpass through, in which the transparent plate does not exist at the lightpassing portion.

The second reflection mirror 9 is made from a parallel plate such as aglass plate. The reflection face 9 a, used as a reflection mirror, canbe formed on one face of the second reflection mirror 9 by depositingsilver film or dielectric multilayer such as aluminum layer on one faceof the second reflection mirror 9. The second reflection mirror 9 isretained in the supporter 30 by the retaining part 34 while theretaining part 34 retains a non-reflection side of the second reflectionmirror 9 without blocking the light path of light. By using one singlefirst reflection mirror 10 and one single second reflection minor 9,positional adjustment of light focus point can be conducted easilycompared to a configuration providing a reflection mirror for each oneof the light sources.

The light beams emitted from the light sources 11-1 to 11-10 of thelight source assembly 2 efficiently enter the respective coupling lenses12-1 to 12-10 and become substantially parallel light or substantiallycondensed light and then the light beam pass through the condensing lensL1.

The light beam passing through the condensing lens L1 is reflected bythe reflection face 10 a of the first reflection mirror 10 toward thecoupling lenses 12-1 to 12-10, and enters the second reflection mirror 9disposed at a position closer to the light source assembly 2 compared toa position of the first reflection mirror 10 as shown in FIG. 1. Then,the light beam is further reflected at the reflection face 9 a of thesecond reflection mirror 9 toward the first reflection mirror 10, andguided to the reflection face 10 a of the first reflection mirror 10.

In this case, the number of light reflection times between the firstreflection mirror 10 and the second reflection mirror 9 is set to onetime, and after such reflection, the light exits from the opening part10 b of the first reflection mirror 10, which is used as a light passingportion. If the number of light reflection times between the firstreflection mirror 10 and the second reflection mirror 9 is set to aplurality of times, the light is repeatedly reflected between thereflection face 10 a of the first reflection mirror 10 and thereflection face 9 a of the second reflection mirror 9 for the pluralityof times, and then the light exits from the opening part 10 b of thefirst reflection mirror 10.

In the above configuration, the light emitted from each of the lightsources 11-1 to 11-10 enters the condensing lens L1 and is refracted bythe condensing lens L1, and then exits the condensing lens L1 toward thereflection face 10 a of the first reflection mirror 10, and then entersthe reflection face 10 a. The light that has entered the reflection face10 a is reflected by the reflection face 10 a toward the secondreflection mirror 9, and then reflected by the reflection face 9 a ofthe second reflection mirror 9 toward the first reflection mirror 10(first reflector), and then enters the first reflection mirror 10. Then,the light reflected to the first reflection mirror 10 (first reflector)from the reflection face 9 a of the second reflection mirror 9 (secondreflector) exits from the opening part 10 b of the first reflectionmirror 10 as shown in FIG. 3A.

In the above described configuration, the light emitted from the lightsources 11-1 to 11-10 becomes closer about the optical axis of thecondensing lens L1 at a reflection position on the reflection face 9 aof the second reflection mirror 9 (second reflector) compared to areflection position on the reflection face 10 a of the first reflectionmirror 10 (first reflector). In the first example embodiment, the numberof light reflection times by each of the first reflection mirror 10 andthe second reflection mirror 9 is set to one time.

As above described, the light beams emitted from the plurality of lightsources 11-1 to 11-10 reflect for a given number of times, for example,one time or a plurality of times between the first reflection mirror 10and the second reflection mirror 9, with which a distance forsynthesizing light beams emitted from the light sources 11-1 to 11-10can become shorter, and the light source unit 1 can be compact in size.The synthesized light beams can become a light beam flux K whilereducing its cross-section area, by which the light density of the lightbeam flux K can be increased, with which the light beam flux K havinghigh light intensity can be emitted.

Further, in the first example embodiment, light beams emitted from thelight sources 11-1 to 11-10 enter the condensing lens L1 collectivelyeven if an attachment position of each of the light sources 11-1 to11-10 and the coupling lenses 12-1 to 12-10 have fluctuation due totolerance, with which fluctuation of the light focus point can besuppressed, in which an adjustment mechanism for each of the lightsources and coupling lens is not required, and adjustment process can besimplified and the cost of light source unit can be reduced. Therefore,an adjustment mechanism for each of the light sources and couplinglenses is not required, and adjustment process can be simplified and thecost of light source unit can be reduced.

Further, light beams emitted from the light sources 11-1 to 11-10 enterthe condensing lens L1 obliquely and become closer to the center part ofthe first reflection mirror 10 when passing through the condensing lensL1 due to the refraction effect of the condensing lens Li, with whichthe light beams can be synthesized with a shorter distance.

In a configuration of FIG. 3, the number of light reflection times atthe first reflection mirror 10 and the second reflection mirror 9 is setto one time.

Further, the number of light reflection times at the first reflectionmirror 10 and the second reflection mirror 9 can be set to a pluralityof times by adjusting a focal distance of the condensing lens L1. Inthis configuration, the light emitted from the light sources 11-1 to11-10 is condensed and refracted by the condensing lens Li, and then thelight is repeatedly reflected between the reflection face of the firstreflection mirror 10 and the reflection face of the second reflectionmirror 9, and then the light exits from the light passing portion formedat the center portion of the first reflection mirror 10. If the light isrepeatedly reflected between the first reflection mirror 10 and thesecond reflection mirror 9 for a plurality of times, a distance forsynthesizing the light beams emitted from the light sources 11-1 to11-10 can be shortened. Further, compared to a cross-section area oflight flux K corresponding to the one time reflection of light, across-section area of light flux K corresponding to the plurality ofreflection times can be reduced, with which the density of light flux Kcan be increased, and light flux having high luminance can be emitted,and further the size of light source unit or apparatus can be reduced.

FIG. 4 is a schematic side view of a light source unit 1A according to asecond example embodiment. Different from the first example embodiment,the light condensing optical system of the second example embodimentincludes a plurality of condensing lens. Specifically, the lightcondensing optical system includes a condensing lens L1 and a condensinglens L2 facing the condensing lens Li. In the second example embodiment,the number of light reflection times at each of the first reflectionmirror 10 and the second reflection mirror 9 is set to one time.

When the light source unit 1A has two lenses such as the condensinglenses Li and L2, compared to the first example embodiment, radius ofcurvature of each one of lenses can be set small compared to the firstexample embodiment, with which spherical aberration can be suppressed.Therefore, even if positions of light emitting points of the lightsources 11-1 to 11-10 and positions of the coupling lenses 12-1 to 12-10fluctuate due to tolerance, fluctuation of the light focus point can bereduced.

In the second example embodiment, two lenses such as the condensinglenses L1 and L2 are used, but the number of lenses can be three ormore. By increasing the number of lenses, spherical aberration can befurther suppressed, and therefore, even if positions of light emittingpoints of the light sources 11-1 to 11-10 and positions of the couplinglenses 12-1 to 12-10 fluctuate due to tolerance, fluctuation of thelight focus point can be further suppressed.

FIG. 5 is a schematic side view of a light source unit 1B according to athird example embodiment. The light source unit 1B has a lightcondensing optical system employing a plurality of lenses such as thecondensing lenses LI and L2 which are faced with each other as shown inFIG. 5. In the third example embodiment, the number of light reflectiontimes at each of the first reflection mirror 10 and the secondreflection mirror 9 is set to two times.

If the light source unit 1B has the light condensing optical systememploying the condensing lenses L1 and L2 and the number of lightreflection times between the first reflection mirror 10 and the secondreflection mirror 9 is set to a plurality of times, compared to theone-time reflection, the power of the condensing lens L1 required tocondense the light beams from the light source assembly 2 to one pointcan be set smaller. Therefore, spherical aberration can be set small,and even if positions of light emitting points of the light sources 11-1to 11-10 and positions of the coupling lenses 12-1 to 12-10 fluctuatedue to tolerance, fluctuation of the light focus point can be furtherreduced.

A description is given of a configuration to suppress fluctuation of thelight focus point in the first example embodiment, the second exampleembodiment and the third example embodiment. FIG. 6 shows a light pathwhen a coupling lens of a light source of the light source unit 1(FIG. 1) of the first example embodiment is shifted for 0.5 mm towardthe inside of the light source unit 1 (synthesizing direction of aplurality of light fluxes). FIG. 7 shows a light path when a couplinglens of a light source of the light source unit 1A (FIG. 4) of thesecond example embodiment is shifted for 0.5 mm toward the inside of thelight source unit 1A (synthesizing direction of a plurality of lightfluxes). FIG. 8 shows a light path when a coupling lens of a lightsource of the light source unit 1B (FIG. 5) of the third exampleembodiment is shifted for 0.5 mm toward the inside of the light sourceunit 1B (synthesizing direction of a plurality of light fluxes). Theseshifts of the coupling lenses assume fluctuation of the coupling lenses.

FIGS. 9 to 11 show irradiation profiles at the light focus point for thelight source unit 1 (first example embodiment), the light source unit 1A(second example embodiment) and the light source unit 1B (third exampleembodiment) with or without shifting of the coupling lens. FIGS. 9A,10A, and 11A respectively show irradiation profiles at the light focuspoint for the light source units shown in FIGS. 3, 4 and 5, in whichtolerance of design is not considered. FIGS. 9B, 10B, and 11Brespectively show irradiation profiles irradiation profile at the lightfocus point for the light source units shown in FIGS. 6, 7 and 8 whenshifting for 0.5 mm, in which tolerance of design is not considered.

The irradiation profiles shown in FIGS. 9 to 11 are prepared bypreparing a mode of each of the light source units on computer programand simulating the irradiation profile on a light condensing face 4 andplotting data. For the simplicity of drawing, FIGS. 9 to 11 show onlytwo light sources and two coupling lenses such as the light sources 11-1and 11-6, and coupling lens12-1 and 12-6 symmetrically disposed withrespect to the x-axis. Further, in cases of FIGS. 9 to 11, a distancefrom the light sources to the light focus point is set with the samedistance.

As shown in FIG. 9A, when there is no shifting (i.e., no deviation) inthe first example embodiment, light beams from the plurality of lightsources are focused at one point, and the beam diameter is about 2 mm.However, as shown in FIG. 9B, when there is shifting (i.e., deviation),light beams from the plurality of light sources are not focused at onepoint, in which each of the light focus point positions are deviatedwith each other, and the light focus point positions have a width ofabout 16 mm.

As shown in FIG. 10A, when there is no shifting (i.e., no deviation) inthe second example embodiment, light beams from the plurality of lightsources are focused at one point, and the beam diameter is about 1 mm.However, as shown in FIG. 10B, when there is shifting (i.e., deviation),light beams from the plurality of light sources are not focused at onepoint, in which each of the light focus point positions are deviatedwith each other, and the light focus point positions have a width ofabout 14 mm.

As shown in FIG. 11A, when there is no shifting (i.e., no deviation) inthe third example embodiment, light beams from the plurality of lightsources are focused at one point, and the beam diameter is about 2 mm.However, as shown in FIG. 11B, when there is shifting (i.e., deviation),light beams from the plurality of light sources are not focused at onepoint, each of the light focus point positions are deviated with eachother, and the light focus point positions have a width of about 2.6 mm.

Based on these irradiation profiles for the light focus point, comparedto the first example embodiment using one condensing lens, the secondexample embodiment using a plurality of condensing lenses can suppressfluctuation of the light focus point because, by using a plurality ofcondensing lenses such as two, radius of curvature per one condensinglens can be set smaller than radius of curvature of the first exampleembodiment. Therefore, spherical aberration can be suppressed, and evenif positions of light emitting points of the light sources 11-1 to 11-10and positions of the coupling lenses 12-1 to 12-10 fluctuate due totolerance, fluctuation of the light focus point can be reduced. Withthis configuration, the light can be efficiently guided to an opticalsystem after the light focus point, with which a light-transmissionoptical system having high efficiently can be devised. With thisconfiguration, the light can be efficiently guided to an optical systemafter the light focus point, with which a light-transmission opticalsystem having high efficiently can be devised.

In the second and third example embodiments, the number of condensinglenses is set two such as the condensing lenses L1 and L2, but thenumber of condensing lenses can be two or more. With this configurationusing a plurality of condensing lenses, spherical aberration of lensescan be further suppressed, and even if positions of light emittingpoints of the light sources 11-1 to 11-10 and positions of the couplinglenses 12-1 to 12-10 fluctuate due to tolerance, fluctuation of thelight focus point can be reduced.

Further, when light profile of light focus point of the second exampleembodiment shown in FIG. 10 and light profile of light focus point ofthe third example embodiment shown in FIG. 11 are compared, even ifshifting occurs, fluctuation of light focus point of the third exampleembodiment can be suppressed significantly. This could be devised due tothe configuration of the third example embodiment, in which the numberof reflection times of light, emitted from the plurality of lightsources, at each of the first reflection face of the first reflector 10and the second reflection face of the second reflector 9 is a pluralityof times such as two, with which light emitted from the plurality oflight sources can be condensed efficiently.

Therefore, under a condition that a distance from the light sources 11-1to 11-10 to the light condensing face 4 is a fixed distance, it ispreferable to set the number of reflection times of light at each of thefirst reflector 10 and the second reflector 9 to a greater number.

In the above described each of the light source units, the lightreflected by the first reflection mirror 10 and the second reflectionmirror 9 exits from the center portion of the first reflection mirror 10as the light flux K, but the exit position of light such as the openingpart 10 b used as the light passing portion is not limited to the centerportion of the first reflection mirror 10. Further, a position of thesecond reflection mirror 9 is not limited to the center portion of thesupporter 30. The position of the light passing portion and the positionof the second reflection mirror 9 can be changed depending on an exitdirection and angle.

In the above described each of the light source units, the couplinglenses 12-1 to 12-10 and the light sources 11-1 to 11-10 are co-axiallydisposed, but the coupling lenses 12-1 to 12-10 can be disposedeccentrically with respect to the optical axis of each of the lightsources. With this configuration, the light beams emitted from the lightsources become converging light having reduced its cross-section areaafter exiting the coupling lenses 12-1 to 12-10, and compared to aco-axial configuration, the power of the condensing lens L1 can be setsmaller, which is preferable.

In the above described each of the light source units, the light sourceassembly 2 employs a concentric circular pattern about the optical axisof the condensing lenses L1, and L2, but other arrangement can be used.For example, the light source assembly 2 can employ a semicircular arcpattern, which is one type of concentric circular pattern, or the lightsource assembly 2 can employ a rectangular pattern. Further, thediameter of the light source assembly 2 is not limited to a diametershown in drawings. For example, by decreasing the diameter of the lightsource assembly 2, the size in the x-direction and the y-directionperpendicular to the z-direction of the light source unit (i.e., opticalaxis direction) can be reduced, with which the light source unit, alighting apparatus, and an image projection apparatus, to be describedlater, can be compact in size.

A description is given to parameters of optical systems of the first tothird example embodiments. Face-to-face distance of each parts in thefirst to third example embodiments are defined as shown in FIGS. 12, 13,and 14. Further, when a lens is convex to −z direction, the radius ofcurvature is defined+, and a face of lens at −z side is defined as R1,and an opposite face of R1 is defined as R2. Further, the face-to-facedistance between lenses is a distance between the curvature center axisof the lenses.

Because the first example embodiment uses one condensing lens,parameters are put in L1 section. Further, al indicates a height in they-direction from the light focus point to light emitting points of thelight sources.

Tables 1 to 6 show face-to-face distance, radius of curvature,thickness, refractive index, and Abbe number for the first to thirdexample embodiments.

TABLE 1 face-to-face distance (mm) 1^(st) example 2^(nd) example 3^(rd)example embodiment embodiment embodiment a1 26.00 a2 4.80 a3 2.07 a414.10 4.7 4.10 a5 15.00 4.00 a6 19.00 15.00 a7 19.00

TABLE 2 radius of curvature (mm) 1^(st) example 2^(nd) example 3^(rd)example embodiment embodiment embodiment Coupling lens R1 16.99 Couplinglens R2 −4.21 Condensing lens 70.00 60.00 80.00 (L1) R1 Condensing lens−459.80 −400.00 −459.80 (L1) R2 Condensing lens −120.00 −124.52 (L2) R1Condensing lens −206.88 −193.91 (L2) R2

TABLE 3 thickness (mm) 1^(st) example 2^(nd) example 3^(rd) exampleembodiment embodiment embodiment Coupling lens 3.00 Condensing lens10.90 11.5 (L1) Condensing lens 5.4 (L2)

TABLE 4 refractive index 1^(st) example 2^(nd) example 3^(rd) exampleembodiment embodiment embodiment Coupling lens 1.52 Condensing lens 1.68(L1) Condensing lens 1.49 (L2)

TABLE 5 Abbe number 1^(st) example 2^(nd) example 3^(rd) exampleembodiment embodiment embodiment Coupling lens 63.50 Condensing lens55.34 (L1) Condensing lens 70.24 (L2)

A description is given of a lighting apparatus and an image projectionapparatus having any one of the above described light source units. FIG.15 is a schematic configuration of an image projection apparatus such asa projector 200 having a lighting apparatus 100.

The lighting apparatus 100 can use any one of the above described lightsource units 1, 1A, and 1B of the first to third example embodiments asthe light source unit. If any one of the light source units 1, IA, and1B, which are compact in size is applied, the lighting apparatus 100 andthe projector 200 can be compact in size. For example, when the lightsource unit 1B of the third example embodiment, which reflects the lightbeams from the light sources between the first reflection mirror 10 andthe second reflection mirror 9 for a plurality of times, is used, a sizeof unit to synthesize light beams can be compact in size in the opticalaxis direction (z-direction in FIG. 15), and resultantly, the lightingapparatus 100 and the projector 200 can be compact in size.

As shown in FIG. 15, the projector 200 includes, for example, a powersource unit 100 having the light source unit 1, a rod integrator 201used as a light quantity equalizing unit, an image generation panel 203,a relay lens 202 and a projection lens 204. The relay lens 202 is usedas a light transmission optical system to transmit light equalized itslight intensity by the rod integrator 201 to the image generation panel203. The projection lens 204 is used as a projection optical system toenlarge and project an image generated by the image generation panel203.

In a case of FIG. 15, the image generation panel 203 of the projector200 is a pass-through type panel that generates images based onmodulation signals, but other panels such as reflection type panel and adigital micro mirror device (DMD) panel can be used. Further, the rodintegrator 201 is an example of the light quantity equalizing unit, andother light quantity equalizing units can be used. Further, the relaylens 202 is one example of the light transmission optical system, andthe projection lens 204 is one example of the projection optical system.

In the lighting apparatus 100, the light source unit is used to emit aplurality of color lights, and among the plurality of colors, the lightsource unit generates and emits at least one color light. Specifically,the lighting apparatus 100 includes, for example, the light source unit1, coupling lenses 421 and 422, a light source unit 440, a coupling lens441, a mirror 204, dichroic mirrors 208 and 442, areflection/passing-through wheel 400 having a passing-through area and areflection area, and a fluorescent material wheel 207.

The light source unit 1 emits, for example, light having a wavelength Aof blue while the light source unit 440 emits, for example, light havinga wavelength C of red, which is different from the wavelength A.Further, for example, the dichroic mirror 442 reflects the light havingthe wavelength A and passes through light having other wavelength, andthe dichroic mirror 208 reflects a light having a wavelength B andpasses through light having other wavelength.

A description is given of a light path of light having the wavelength Aand emitted from the light source unit 1. When the reflection area ofthe reflection/passing-through wheel 400 is on the light path of thelight having the wavelength A, the light enters thereflection/passing-through wheel 400 and is then reflected with a givenangle. The light having the wavelength A is reflected and exit from thereflection/passing-through wheel 400, and then passes the coupling lens421, and is then reflected at the dichroic mirror 442 with a givenangle, and passes the dichroic mirror 208, and then enters the rodintegrator 201.

When the passing-through area of the reflection/passing-through wheel400 is on the light path of the light having the wavelength A, the lightenters the reflection/passing-through wheel 400 and then passes thereflection/passing-through wheel 400 and then enters the minor 204 viathe coupling lens 422. Then, the light is reflected at the mirror 204with a given angle, and then passes the dichroic mirror 208, and thenenters the fluorescent material wheel 207. The light having thewavelength A that has entered the fluorescent material wheel 207 isirradiated to fluorescent material 231 via light condensing element 230.

The fluorescent material 231 is excited by the light having thewavelength A and emits the light having the wavelength B longer than thewavelength A. The light having the wavelength B is reflected by a plate232, and then enters the dichroic mirror 208 via the light condensingelement 230 and is reflected by the dichroic mirror 208 with a givenangle, and enters the rod integrator 201. The fluorescent material 231may be formed on an entire periphery of the fluorescent material wheel207 as a ring pattern.

Light having the wavelength C emitted from the light source unit 440enters the dichroic mirror 442 via the coupling lens 441. The lighthaving the wavelength C passes the dichroic mirror 442, and furtherpasses the dichroic mirror 208, and then enters the rod integrator 201.Each light that has entered the rod integrator 201 exits to the relaylens 202, and then irradiated to the image generation panel 203 via therelay lens 202, and is then projected on an external screen using theprojection lens 204.

By employing any one of the above described light source units for theprojector 200, the light beams emitted from a plurality of light sourcescan be synthesized as the light beam flux K having high light intensitywith reduced cross-section area, and the incidence angle to the rodintegrator 201 can be set smaller. Therefore, an area of the lightradiating on the image generation panel 203 can be reduced, by which theprojection lens 204 having a smaller numerical aperture (NA), whichmeans a greater F-number lens, can be used. Therefore, the projectionlens 204 can be designed and manufactured easily, and imagingperformance can be maintained at a good enough level easily. The abovedescribed image projection apparatus 200 can be compact in size whileusing a plurality of light sources and equalizing the light intensity.

The above described light source units 1, 1A, and 1B can be applied tothe lighting apparatus 100 and other apparatuses. For example, the abovedescribed light source units 1, 1A, and 1B can be applied to a lightingapparatus that uses light emitted from the light source unit only as anexcitation light to hit fluorescent material, or an image projectionapparatus having this lighting apparatus. Further, for example, lightemitting diodes (LEDs) can be used as red and blue light, andfluorescent light, which is generated by using excitation light of theabove described light source units, can be used as green light.

In the above described example embodiments, the light source unit usingthe plurality of light sources can be compact in size with an enhanceduse efficiency of light from the light sources without increasing thesize of the optical system, and the lighting apparatus and the imageprojection apparatus using the above described light source unit can becompact in size.

In the above described example embodiments, the light beams emitted fromeach of the plurality of light sources is refracted by the lightcondensing optical system, and reflected at the reflection faces of thefirst reflector 10 and the second reflector 9, and a reflection positionof second reflector 9 is close to an optical axis of the lightcondensing optical system such as the condensing lens compared to areflection position of the first reflector 10. Further, as abovedescribed, the light beams emitted from the plurality of light sourcesreflect for a given number of times, for example, one time or aplurality of times between the plurality of reflection faces of thereflection mirrors, with which a distance for synthesizing light beamsemitted from the light sources can be shorter, and the light source unitcan be compact in size. Therefore, the image projection apparatus havingthe above described high efficient and compact light source unit can becompact in size.

Numerous additional modifications and variations are possible in lightof the above teachings. It is therefore to be understood that within thescope of the appended claims, the disclosure of the present inventionmay be practiced otherwise than as specifically described herein. Forexample, elements and/or features of different examples and illustrativeembodiments may be combined each other and/or substituted for each otherwithin the scope of this disclosure and appended claims.

What is claimed is:
 1. A light source unit comprising: a first reflectorhaving a reflection face; a second reflector having a reflection face; aplurality of light sources; and a light condensing optical system tocondense light emitted from the plurality of light sources wherein lightbeams emitted from the plurality of light sources are reflected at afirst reflection position on the reflection face of the first reflector,and then reflected at a second reflection position on the reflectionface of the second reflector, wherein the second reflection position isclose to an optical axis of the light condensing optical system comparedto the first reflection position.
 2. The light source unit of claim 1,wherein the plurality of light sources is disposed around the firstreflector when viewed from a light exiting face side, wherein thereflection face of the first reflector and the reflection face of thesecond reflector are disposed by facing the reflection face of the firstreflector and the reflection face of the second reflector with eachother, wherein the light beams emitted from the plurality of lightsources enter the light condensing optical system, then exit to thereflection face of the first reflector via the light condensing opticalsystem, then reflected to the light condensing optical system at thereflection face of the first reflector, then reflected at the reflectionface of the second reflector to the first reflector, and then exit tothe first reflector.
 3. The light source unit of claim 1, wherein thelight condensing optical system includes a plurality of condensinglenses.
 4. The light source unit of claim 1, wherein the number ofreflection times of light, emitted from the plurality of light sources,at each of the first reflection face of the first reflector and thesecond reflection face of the second reflector is one time.
 5. The lightsource unit of claim 1, wherein the number of reflection times of light,emitted from the plurality of light sources, at each of the firstreflection face of the first reflector and the second reflection face ofthe second reflector is a plurality of times.
 6. The light source unitof claim 1, wherein the first reflector is made from a parallel platehaving a center portion that can pass light.
 7. The light source unit ofclaim 1, wherein the plurality of light sources is a plurality of laserelements combined with a plurality of coupling lenses that convertslight emitted from the laser elements to parallel light or converginglight, the plurality of laser elements combined with a plurality ofcoupling lenses are configured as a light source assembly.
 8. A lightingapparatus for emitting lights of a plurality of colors comprising: thelight source unit of claim 1, wherein the light source unit generatesand emits light of at least one of colors of the plurality of colors. 9.An image projection apparatus comprising: the lighting apparatus ofclaim 8.